Medical image processing Medical image processing and finite element analysisand finite element analysis

András HajduAndrás Hajdu

UNIVERSITY OF UNIVERSITY OF DEBRECENDEBRECENHUNGARYHUNGARY

SSIP 2003July 3-12, 2003

Timişoara, Romania

MEDIPMEDIPPlatformPlatform independent software system independent software system for medical imagefor medical image processingprocessing

The aim of the project is to develop an informatical background

to theoretical and applied studies in the field of multi-modal medical image processing,

which results may lead tomarketable products.

MEDIPMEDIPPlatformPlatform independent software system independent software system for medical imagefor medical image processingprocessing

Department of Information Technology,University of Debrecen

PET Center, University of Debrecen

Mediso Medical Imaging System Ltd.

Developers

Department of Orthopedic Surgery,University of Debrecen

Faculty of Health Sciences, Chair of Radiotherapy,Semmelweis University

Faculty of Medicine Dept. of Radiology and Oncotherapy,Semmelweis University

Test partners

MEDIPMEDIPPlatformPlatform independent software system independent software system for medical imagefor medical image processingprocessing

01.200401.200301.2002

finished sessions

current session

future sessions

1. Survey, problem specification

2. Modelling, system plans

3. Implementation

4. Implementation,optimisation

5. Fine tuning,testing, presentation

SesSes11 Ses2Ses2 Ses3Ses3 SesSes44 SesSes55

Dependence

Feedback

Pert diagram

MEDIPMEDIP – Demostration programs – Demostration programsPlatformPlatform independent software system independent software system for medical imagefor medical image processingprocessing

Finite element modellingfor virtual surgery

Selection of volume of interest based on image fusion

4D visualization of gated heart and lung inspections

Dept. of Information Tech., UD

Dept. of Orthopaedy, UD

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Demonstration program

Finite element modeling for virtual surgery

Connecting to theConnecting to the b base librariesase libraries FFileile I/O I/O (DICOM) (DICOM) Segmentation techniquesSegmentation techniques Contour tracking, ROI selectionContour tracking, ROI selection Morphological operationsMorphological operations Complex GUIComplex GUI ROI and VOI ROI and VOI 2D/3D 2D/3D visualizationvisualization 3D geometric navigation3D geometric navigation PrintingPrinting

Demonstration program

Finite element modeling for virtual surgery

Demonstration program

FEM surgery planning frame program

Login (database opening)

Launching (opening new/existing profile)

DICOM file importImage manipulation (morphological filtering)

Creating geometric model

Segmentation (automatic/manual)

FEM contact

Adjusting parameters

Demonstration program

Surgery planning (virtual osteotomy)

3D visualization, selecting VOI

Surgery planning (virtual osteotomy)Surgery planning (virtual osteotomy)

Case studyCase study

Zoltán CsernátonyZoltán Csernátony, Department of Orthopaedics, UD, Department of Orthopaedics, UDSzabolcs Molnár, Department of Orthopaedics, UDSzabolcs Molnár, Department of Orthopaedics, UDSándor ManóSándor Manó, College Faculty of Engineering, UD, College Faculty of Engineering, UDAndrásAndrás HajduHajdu, Institute of Informatics, UD, Institute of Informatics, UDZoltánZoltán ZörgőZörgő, Institute of Informatics, UD, Institute of Informatics, UD

ANALYZIS OF A NEW FEMUR ANALYZIS OF A NEW FEMUR LEGTHENING SURGERYLEGTHENING SURGERY

LowerLower extremityextremity inequalityinequality

Shorter femur Shorter tibia

Handling the problem (I.)Handling the problem (I.)

Orthopaedic shoes

Handling the problem (II.)Handling the problem (II.)

Surgical intervention(after Wagner and Ilizarov)

cutting distancing ossification

!

A new lengthening methodA new lengthening method

Torsion and angulation could also be correnced

Potencial instrumentationPotencial instrumentation

In the past there existed no way of In the past there existed no way of testing new interventions but to try it out testing new interventions but to try it out in vivoin vivo

This days technology makes is possible This days technology makes is possible to test and adjust new operative to test and adjust new operative interventions before even one cut is interventions before even one cut is mademade

Past and presentPast and present

Validating new ideasValidating new ideas

Laboratory tests Finite element analysis

How can we use FEM/FEA?How can we use FEM/FEA?

CT slicesimage

processinggeometrical

reconstruction

Building up a basic modelBuilding up a basic model

Importing images in Importing images in CT CT firmware format firmware format (DICOM)(DICOM)

Image enhancement (sharpening, filtering)Image enhancement (sharpening, filtering) Extracting ROIsExtracting ROIs

Building up a basic modelBuilding up a basic model Applying contour splines (Euclidean geometry)Applying contour splines (Euclidean geometry)

Reconstructing solid model (Coons patches)Reconstructing solid model (Coons patches)

Modeling intervention Modeling intervention geometry (I.)geometry (I.)

Based on the path of the cutting toolBased on the path of the cutting tool

We need to determine:We need to determine: Cutting thicknessCutting thickness PitchPitch Ending hole parametersEnding hole parameters

Modeling interventionModeling interventiongeometry (II.)geometry (II.)

We subtract the object representing We subtract the object representing the the „„removed tissueremoved tissue” ” from the femur modelfrom the femur model

Modeling intervention Modeling intervention physicsphysics The bone tissue should be The bone tissue should be

modeled as a very complicated modeled as a very complicated nonlinear anisotropic materialnonlinear anisotropic material

We are using linearWe are using linear elasticelastic izotropicizotropic andand orthotropicorthotropicmaterial models insteadmaterial models instead

We mesh the modelWe mesh the model One end is fixed, on the other end One end is fixed, on the other end

a traction force is applieda traction force is applied How big is the evolved stress? How big is the evolved stress?

How much elongation can it How much elongation can it support?support?

Some resultsSome results

There exists an optimal combination of parameter values

2 3

6,00 249 730 000 223 490 000

7,00 222 730 000 231 270 000

8,00 263 800 000 247 180 000

2 36,00 499 460 000 446 990 0007,00 445 460 000 462 530 0008,00 527 600 000 494 370 000

2 36,00 749 190 000 670 480 0007,00 668 190 000 693 800 0008,00 791 400 000 741 550 000

2 36,00 998 910 000 893 970 0007,00 890 920 000 925 060 0008,00 1 055 200 000 1 995 000 000

2 36,00 1 248 600 000 1 117 500 0007,00 1 113 700 000 1 156 300 0008,00 1 319 000 000 1 570 000 000

Min (Best)Max (Worst)

rem

ain

ing

tissu

e

(mm

)

cutting thickness (mm)Equivalent stress (von Misses)Pa

1 mm elongation case

2 mm elongation case

3 mm elongation case

4 mm elongation case

5 mm elongation case

The greatest stress values evolve near the The greatest stress values evolve near the ending holes. ending holes.

The inward oriented conical bore appears to be The inward oriented conical bore appears to be the most suitablethe most suitable

Additional adjustmentsAdditional adjustments

We have built a schematic modelWe have built a schematic model It is a cylindrical pipe with inner and It is a cylindrical pipe with inner and

outer diameters equaling the outer diameters equaling the femur’s average diametersfemur’s average diameters

The same analysis were performedThe same analysis were performed

• The stress values measured on the pipe-model were 1.61 (D=0.27) times lower under same conditions• There was a 91% correlation between the two datasets

Checking the resultsChecking the results

Future plansFuture plans

More precise material modeling by using More precise material modeling by using cylindrical layers, and other element typescylindrical layers, and other element types

In-vitro lab tests based on the resultsIn-vitro lab tests based on the results

Thank you for your attention.Thank you for your attention.